Ryne asked:

Hawking says that even what we take reality to be in science is shaped by theory. A couple of my friends are going back and forth as to if this is true or false. What’s your opinion?

Answer by Craig Skinner

It is true that we take reality to be as our best theories suggest, and its entities to be those postulated by such theories. And so we should.

Scientists intend and hope that their theories do describe reality. And, if a theory is well-tested and generally accepted, we do indeed take reality to be as the theory says.

Furthermore, I think reality often is as we so take it. In short, I think some of our best theories are true.

Of course, no theory can be proven to be true (a later improved theory may explain all that our current one does and also things our current one doesn’t). Nor, strictly, can any theory be proven to be false (all theories are tested along with auxiliary hypotheses as a package, and we can always salvage the theory when one of its predictions proves incorrect, by discarding an auxiliary hypothesis). Science, unlike mathematics, is not in the business of proof.

But don’t let these philosophical points persuade you to the view that just as past theories were mostly wrong (stock examples: phlogiston theory; caloric theory; the luminiferous ether; Newton’s gravity replaced by Einstein’s), so our present theories will eventually turn out also to be wrong, and therefore what we take reality to be is always wrong. Some current theories will turn out to be wrong (see below), but with others there is just no chance of this.

For example, it wont turn out that DNA is not the genetic material in cells or that the coding for amino acids doesn’t depend on the base sequence along the DNA strands. Nor will the periodic table of the elements, and its account of chemical properties depending on the number and arrangement of electrons in the atoms, turn out to be wrong. Nor will it be shown that planets don’t orbit the Sun in elliptical paths. Or that the Sun (and other stars) is not a huge nuclear fusion reactor.

On the other hand, very fundamental physical and cosmological theories are less secure, and leave us unsure as to how to take reality to be:

What are the ultimate constituents of matter? Successive versions of atomism have suggested tiny indivisible corpuscles, then mostly-empty-space atoms with tiny nuclei and shells of electrons, then nuclei composed of protons/neutrons, then these in turn composed of quarks, now speculations (no good theory yet) that all these (and other) apparently fundamental particles are composed of miniscule strings or loops, or even that ultimately they are all just parts of immaterial fields, in turn reducible to numbers or sets so that matter isn’t even material.

What is the reality behind quantum mechanics? Is consciousness necessary to collapse probability wave functions and produce definite states of affairs, or is there no collapse and instead endless proliferation of Everettian parallel realities, or are things yet some other way. We just don’t know.

Furthermore, our two best fundamental physical theories, general relativity and quantum mechanics, each wonderfully well-confirmed in its domain, are incompatible at the level of the very small, so that one or both must be wrong, and the search for a quantum theory of gravity continues.

To focus on the cosmos now, rather than the microworld, The Big Bang origin of our universe is a well-established theory, so that we can safely say we live in an expanding universe containing visible matter, energy, so-far-mysterious dark matter, and maybe even-more-mysterious dark energy. But as to whether our universe is the only one or merely one of a vast ensemble (multiverse) we don’t know. Neither do we know what set off the Big Bang, nor why a universe exists rather than nothing at all.

So, whilst certainty, proof and infallibility elude us, we are definitely justified in taking many aspects of reality to be as theory says, although there are, and maybe always will be, some aspects beyond our grasp.

I have dealt with reality as being the natural world including the biosphere and the human species.

As to whether reality includes supernatural entities, that is another important matter, but not one for science, although findings of science are relevant to the question. And philosophy-savvy scientists contribute much to the theism/atheism debates (although I am reluctant to count Hawking, even less so Dawkins, as being in this category)